This proposal encompasses 6 collaborative investigations, supported by 3 integrated core facilities, to address issues fundamental to the etiology, pathogenesis and treatment of cardiac failure. The studies are focused in an attempt to unravel the molecular basis underlying cardiac growth and hypertrophy, post ischemic dysfunction following reperfusion and coronary occlusive disease post-transplantation. We will attempt to isolate the genes responsible for two inherited cardiac disorders: hypertrophic cardiomyopathy, whose underlying biochemical defects may also help to clarify mechanisms for acquired cardiac hypertrophy, and myotonic dystrophy, which in contrast, affects particularly the cardiac conduction system. We will clone the human cardiac sodium channel and analyze its structure-function relationships by site-directed mutagenesis and expression in Xenopus oocytes, as a first step toward rational design of anti-arrhythmic drugs which focus on transcriptional control of alpha-actin genes during cardiac myogenesis and hypertrophy, including the isolation of promoter-binding transcription factors that control actin gene expression. In situ hybridization will be used, to identify the expression of each alpha-actin gene in cardiac development, experimental hypertrophy, and clinical failure. We will elucidate the molecular mechanisms responsible for acute cardiac failure following ischemia and reperfusion, using EPR spectroscopy and spin trap agents to quantify the in vivo generation of oxygen-free radicals in the conscious dog, NMR spectroscopy to detect potential toxic metabolites in isolated hearts, and implantable Doppler probes to assess effects of anti-oxidants on ventricular dysfunction in patients after cardiac surgery. Using pigs specially bred for major histocompatibility complex, we will determine the immune and non-immune factors contributing to accelerated atherosclerosis after transplantation. These studies should provide significantly new insights into the molecular basis of cardiac failure and a rational basis for more effective therapy.